Have You Dated This Man?

After a whirlwind romance, Nash, a Minnesota blogger, thought Simon Reid was the man of her dreams. He was a dashing Englishman she'd met on a dating website who described himself as the owner of a construction company. After only a handful of dates over two months, he was talking marriage, and Nash was smitten.

When Reid disappeared one day, Nash was frantic - until she got a call from Reid's wife. She was looking for him too. They could only reflect on his betrayal, as it seemed Reid had run off to England.

But Nash wasn't about to take it lying down.

"I just decided to take matters into my own laptop," she told ABC News. She wrote a scathing post on her blog warning women of the man who had duped her.

"Turns out there is an Anti-Christ," she wrote, "and his name is Simon Reid."

Nash said the post was mostly cathartic, but in the back of her mind, she hoped it might help another woman avoid her fate.

Nash never expected what happened next. She heard from women half-way around the world - women who read her blog too late to avoid dating Simon Reid.

Nash reached out to these other past girlfriends and brought them together. And they concocted a plan to catch Reid red-handed.

Watch the shocking video of what happened on "20/20? Friday, starting at a special time, 9 p.m. ET.